1. Field of the Invention
The present invention relates to scanning electron beam apparatus and methods of using scanning electron beam apparatus.
2. Description of the Background Art
As technology progresses in the semiconductor industry, the features of integrated circuit devices are being reduced to smaller and smaller sizes. Such reduction in feature size enables a greater density of devices to be manufactured on a semiconductor. However, increasingly smaller feature sizes require increasingly higher resolutions and accuracy in measurement, inspection, and review equipment.
One category of such equipment is based on scanning electron microscope (SEM) technology. In an SEM, a beam of electrons (an electron beam or e-beam) is scanned over a specimen, and the resulting electrons that are returned from the specimen surface are used to create an image of the specimen surface, or to acquire a linescan. In order to handle increasingly smaller feature sizes, it is desirable to increase the effective resolution (i.e. the apparent beam width) and/or accuracy of SEM-based equipment used for feature measurement, substrate inspection, or defect review.
The invention relates to a method and system for electron beam scanning for measurement, inspection or review.
In accordance with one embodiment of the invention, the method includes a first scan on a region to collect first image data. The first image data is processed to determine information about a feature in the region. A scanning method is selected for imaging the feature. A second scan using the selected scanning method on the feature is then applied to collect second image data.
In accordance with another embodiment of the invention, the method includes scanning at least one unit of pixels to collect image data. A delay period is then inserted to reduce an electron dosage to the substrate. These steps are repeated.
In accordance with another embodiment of the invention, the method includes scan lines that converge upon a feature on the substrate. The scan lines may be linear (and oriented either in one or two dimensions) or may be shaped in dependence upon a shape of a feature of interest.
In accordance with another embodiment of the invention, the method includes randomly ordered scan units. The randomly ordered scan units may either be randomly ordered scan lines or randomly ordered pixels.
In accordance with another embodiment of the invention, the method includes scan lines proceeding bi-directionally. The scan lines may proceed bi-directionally in one dimension or in two dimensions.
Another embodiment relates to a system for electron beam scanning. The system may include the following: means for a first scan on a region to collect first image data; means for processing the first image data to determine information about a feature in the region; means for selecting a scanning method for imaging the feature; and means for a second scan using the selected scanning method on the feature to collect second image data.